Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546
(OP) 5-201
OP
If Rst CB mon LO By is set to User Interface the a further command appears in the the CB
CONTROL column of the menu, CB mon LO reset. This command can be used to reset the
lockout.
This logic is included in the Figure 113 and Figure 114 (CB Monitoring figure).
An auto-recl
ose lockout state of a circuit breaker will generate an auto-reclose circuit breaker
lockout alarm (AR CBx lockout) and DDB 306 or 328 is set, corresponding to CB1 or CB2
being locked out, as per the logic diagrams in AR Figure 57 and Figure 58.
The auto
-reclose lockout conditions can be reset by various commands and settings options
found under the CB CONTROL column of the menu.
These settings and commands are described below:-
If Res LO by CB IS is set to Enabled, the circuit breaker lockout is reset if the circuit breaker
is manually closed successfully. For this the circuit breaker must remain closed long enough
so that it enters the “In Service” state. (See section 5.4, Circuit Br
eaker In Service and
Figure 109, Figure 110, Figure 111, Figure 112, Figure 113 and Figure 114.
If Res LO
by UI is set to Enabled, the circuit breaker lockout can be reset by the user
interface commands Reset CB1 LO or Reset CB2 LO found in the CB CONTROL column of
the menu.
If Res LO by NoAR is set to Enabled, the circuit breaker lockout can be reset by temporarily
generating an “AR disabled” signal according to the logic described in section 5.6.6.2,
“Auto-re
close Enable” logic and AR Figure 5.
If R
es LO by ExtDDB is set to Enabled, the circuit breaker lockout can be reset by
activation of the relevant input DDB Rst CB1 Lockout or Rst CB2 Lockout (DDB 446 /
1422) mapped in the PSL.
If Res LO by TDelay is set to Enabled, the circuit breaker lockout is automatically reset after
a user defined time delay as set in LO Reset Time setting.
The reset circuit breaker auto-reclose lockout logic is shown in AR Figure 57 and Figure 58
(logi
c diagram supplement).
5.7 Dual circuit breaker system voltage checks (P544/P546)
5.7.1 Dual circuit breaker system checks overview (P544/P546)
In som
e situations it is possible for both “bus” and “line” sides of a circuit breaker to be live
when the circuit breaker is open, for example at the ends of a feeder which has a power
source at each end. Therefore, when closing the circuit breaker, it is normally necessary to
check that the network conditions on both sides are suitable, before giving a CB Close
command. This applies to both manual circuit breaker closing and auto-reclosure. If a
circuit breaker is closed when the line and bus voltages are both live, with a large phase
angle, frequency or magnitude difference between them, the system could be subjected to
an unacceptable shock, resulting in loss of stability, and possible damage to connected
machines.
System checks involve monitoring the voltages on both sides of a circuit breaker, and, if both
sides are live, performing a synchronism check to determine whether the phase angle,
frequency and voltage magnitude differences between the voltage vectors, are within
permitted limits.
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